Virtual Local Area Network | Division of Broadcast Domain

Fig 1: Virtual Local Area Network
VLAN stands for the Virtual Area Network it is defined as the "one broadcast domain divide into the multiples broadcast domains" known as the VLANs. So basically the separation/isolation of the individual broadcast domain into the multiples domains. Let suppose if we have 24 ports switch we separate the ports according to the two sub domains means 1-12 ports are members of VLAN 10 and 13-24 ports are the members of VLAN 20. So these are the two virtual subdomains/Local Area Networks and the fact is that the members of one VLAN not communicate with the other VLAN and if the network of two VLANs are same they don't communicate with each other and if we want to communicate these VLANSs than the concept is Inter VLAN Routing. VLAN act as the like the Local Area Network. VLAN is use to increase the Broadcast domains and by increasing the broadcast domain the size of broadcast domains decrease. VLAN is the concept for the sake of the privacy so the reason of VLAN is to maintain the privacy. VLAN is also very helpful for the policy based switching. VLAN is the alternate of the physical LAN but the difference is it is virtual but the work is same.

By default on every switch there is a VLAN that is the VLAN 1 and all the ports of the switch members of the VLAN 1. And when we create VLAN we write a number of VLAN e.g "VLAN 10" in the global configuration mode basically here we divide the main broadcast of the switch into small broadcasts. So on every switch there are total 1-1005 VLANs so following are the VLANs that are reserved and by default active:

VLAN 1: It is the VALN that active by default all the ports are the members of this.
VLAN 1002: It is the VALN that active by default and it is used for the fddi-default.
VLAN 1003: It is the VALN that active by default and it is used for the token-ring-default.
VLAN 1004: It is the VALN that active by default and it is used for the fddinet-default.
VALN 1005: It is the VALN that active by default and it is used for the trnet-default.

Fig 2: VLANs